Classifications

• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09C—TREATMENT OF INORGANIC MATERIALS, OTHER THAN FIBROUS FILLERS, TO ENHANCE THEIR PIGMENTING OR FILLING PROPERTIES ; PREPARATION OF CARBON BLACK  ; PREPARATION OF INORGANIC MATERIALS WHICH ARE NO SINGLE CHEMICAL COMPOUNDS AND WHICH ARE MAINLY USED AS PIGMENTS OR FILLERS
  • C09C1/00—Treatment of specific inorganic materials other than fibrous fillers; Preparation of carbon black
  • C09C1/0006—Treatment of specific inorganic materials other than fibrous fillers; Preparation of carbon black containing bismuth and vanadium
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
  • C01G31/00—Compounds of vanadium
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
  • C01P2002/00—Crystal-structural characteristics
  • C01P2002/70—Crystal-structural characteristics defined by measured X-ray, neutron or electron diffraction data
  • C01P2002/76—Crystal-structural characteristics defined by measured X-ray, neutron or electron diffraction data by a space-group or by other symmetry indications
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
  • C01P2002/00—Crystal-structural characteristics
  • C01P2002/80—Crystal-structural characteristics defined by measured data other than those specified in group C01P2002/70
  • C01P2002/84—Crystal-structural characteristics defined by measured data other than those specified in group C01P2002/70 by UV- or VIS- data
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
  • C01P2004/00—Particle morphology
  • C01P2004/80—Particles consisting of a mixture of two or more inorganic phases
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
  • C01P2006/00—Physical properties of inorganic compounds
  • C01P2006/12—Surface area
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
  • C01P2006/00—Physical properties of inorganic compounds
  • C01P2006/60—Optical properties, e.g. expressed in CIELAB-values

Definitions

• Bismuth vanadate occurs in nature in an orthorhombic form commonly called pucherite.
• Pucherite is a dull yellow-brown mineral, which is not useful as a pigment.
• Pucherite is similar in color to limonite, a dull yellow-brown iron oxide, which has never been produced as a bright, high intensity pigment despite repeated attempts.
• the present invention relates to a process for preparing pigmentary bismuth vanadate which process comprises mixing a solution of Bi(NO 3 ) 3 .5H 2 O in nitric acid with a solution of alkali vanadate in an aqueous base selected from sodium hydroxide and potassium hydroxide, to precipitate a bismuth vanadate gel suspended in a solution containing dissolved alkali nitrate, wherein the molar ratio of Bi 3+ to VO 4 3- is from about 0.90:1.00 to about 1.10:1.00 and wherein the normalities of the acid and base solutions are adjusted prior to mixing so that the pH of the mixture will be from about 1.0 to about 11.0, preferably from about 1.5 to 4.0; adjusting the pH of the suspension to about 2.2-6.0 with an aqueous base selected from sodium hydroxide and potassium hydroxide if the pH is less than about 2.2, or with an acid selected from nitric acid or sulfuric acid if the pH is greater than about 6.0; removing the gel from
• pigmentary is meant a bismuth vanadate which is bright primrose yellow, single phase monoclinic crystalline as determined by X-ray diffraction, having high intensity, good strength and good lightfastness.
• pigmentary bismuth vanadate is entirely in the monoclinic crystal phase as determined using X-ray diffraction.
• X-ray diffraction measurements are made with a Debye-Scherrer powder camera using Cu K ⁇ radiation from a Norelco Type 12045B unit at 40 kV/20mA and a 6-hour exposure.
• the bismuth vanadate of the present invention exhibits a large increase in reflectance in the range of the visible spectrum from 450 to 525nm which shows that it is primose yellow in color and has high intensity and good strength.
• Reflectance is used herein as a comparison of the specular and diffuse reflectance of a known standard with the sample to be tested using Type I illumination. Reflectance is measured on a Cary Model 14 spectrophotometer equipped with an integrating sphere, painted with Eastman white reflectance paint No. 6080.
• the sample to be tested is prepared by mixing 10 weight percent of the bismuth vanadate of the present invention with 90 weight percent of barium sulfate, Eastman Reflectance Standard No. 6091, until a uniform powder is obtained.
• the reflectance of the known standard, Eastman Reflectance Standard No. 6091 is compared with that of the sample.
• the sample containing the bismuth vanadate of the present invention exhibits an increase of at least about 65 reflectance units on a scale in which the Eastman Reflectance Standard No. 6091 exhibits a reflectance of 100 units over the entire visible spectrum.
• many of the samples exhibit increases in reflectance of at least about 70 units or greater. The greater the magnitude of the change in reflectance within the specified spectral range, the greater the intensity and strength of the sample.
• the intensity and lightfastness of pigmentary bismuth vanadate in a paint are measured from paint drawdowns made to complete hiding.
• the paint is made by dispersing the pigment into a binder in a 2:1 ratio by weight of pigment to binder using a Hoover muller.
• the binder is composed of 98.9 weight percent #2 transparent varnish made by Superior Varnish and Drier Company, Merchantsville, N.J.; 1 weight percent, as lead, of lead Nuodex® drier (contains 24% lead), and 0.1 weight percent, as manganese, of manganese Nuodex® drier (contains 6% manganese).
• the drawdowns are dried for about 72-120 hours in a well-ventilated room at 25° C. and less than about 50% humidity.
• Intensity is determined by the green filter reflectance of a masstone drawdown. Intensity is expressed as a percent of green filter reflectance measured with a Gardiner Multipurpose Reflectometer, Serial. No. 40, (Gardiner Laboratory, Inc., Bethesda, MD), using a white reflectance standard at a setting of 86.1 and light from a General Electric CVS projector lamp passed through the green tristimulus filter supplied with the Gardiner Reflectometer.
• the Gardiner Multipurpose Reflectometer is described in National Bureau of Standards Research Paper RP 1345, dated Nov., 1940, by Richard S. Hunter, and National Bureau of Standards Circular C429, dated July 30, 1942, by Richard S. Hunter.
• the intensity of the bismuth vanadate of the present invention is such that it has a green filter reflectance of at least about 60 percent.
• Lightfastness is determined after the dried paint drawdowns have been continuously exposed for 44 hours in an Atlas Color Fade-Ometer® Type FDA-P.
• a Gardiner Multipurpose Reflectometer is used as described above to measure green filter reflectance before and after exposure. Measurements are taken within one hour prior to exposure and again within one hour after exposure. The percent lowering of reflectance after exposure based on initial reflectance is percent Fade-Ometer® darkening. The lower the percent Fade-Ometer® darkening, the better the lightfastness of the pigment.
• the bismuth vanadate of the present invention will generally exhibit a percent Fade-Ometer® darkening of about 11 percent or less, preferably about 7 percent or less, after 44 hours of exposure.
• the surface area of the bismuth vanadate is about 2-22 m 2 /g.
• a surface area of about 8-22 m 2 /g. is preferred.
• a surface area of about 2-4 m 2 /g. is preferred because of increased heat stability. The surface area is measured on a Perkin-Elmer Shell Model 212C Sorptometer using the technique recommended by the manufacturer.
• pigmentary bismuth vanadate is prepared by mixing a solution of up to about 0.8M Bi(NO 3 ) 3 .5H 2 O in up to about 4.0N nitric acid, preferably about 0.2M Bi(NO 3 ) 3 .5H 2 O in about 1.0N nitric acid, with a solution of alkali vanadate (sodium vanadate or potassium vanadate), preferably up to about 0.32M Na 3 VO 4 , in up to about 1.6N aqueous base selected from sodium hydroxide or potassium hydroxide, more preferably about 0.2M Na 3 VO 4 in about 1.0N sodium hydroxide.
• alkali vanadate sodium vanadate or potassium vanadate
• the molar ratio of Bi 3+ to VO 4 3- can be about 0.90:1.00 to 1.10:1.00, preferably about 0.98:1.00 to 1.05:1.00, which indicates that either an excess of Bi 3+ or VO 4 3- is allowable.
• VO 4 3- is used herein to denote a pentavalent vanadium species in an aqueous solution, but it does not mean a specific pentavalent vanadium species present at a given pH and vanadium concentration.
• the normalities of the acid and base solutions are adjusted prior to mixing so that the pH of the reaction mixture will be about 1.0-11.0.
• a pH of about 1.5-4.0 is preferred because it yields a gel from which a pigmentary monoclinic bismuth vanadate product having optimum intensity and/or lightfastness can be obtained.
• the preferred method of mixing the solutions is in a flow reactor which gives a very rapid incremental combination under high turbulence conditions.
• Incremental combination means that small, essentially stoichiometric quantities are reacted at one time. This prevents relatively large gradients and stoichiometric imbalance that result when large quantities of reactants are mixed at once. Such imbalance results in undesirable side reactions.
• Apparatus which conveniently achieve this result are tee mixers or flow reactors.
• bismuth vanadate gel as used herein means a hydrous, X-ray amorphous bismuth vanadate precipitate containing occluded water.
• the gel should not be removed from the suspension until the pH of the suspension has been stabilized at about 2.2-6.0, preferably about 3.0-3.5.
• the pH of the suspension is less than about 2.2, it may be adjusted upward with aqueous sodium hydroxide or potassium hydroxide, and if it is greater than about 6.0, it may be adjusted downward with an acid selected from nitric acid or sulfuric acid.
• Prompt adjustment of the pH of the suspension to the final range listed above is advisable, although under certain circumstances the bismuth vanadate gel is stable for up to several hours at room temperature prior to pH adjustment.
• the gel is then removed from the suspension, preferably by filtration.
• the gel is collected and, if it contains more than about 10 percent alkali nitrate based on the theoretical yield of bismuth vanadate, the gel must be washed with water until it contains about 10 percent or less.
• the gel When an excess of vanadium is used in the formation of the gel, the gel must be washed prior to the above aqueous digestion to remove any alkali nitrate in excess of 10 percent by weight based on the theoretical yield of bismuth vanadate.
• the suspension containing the gel is then heated at a temperature of from about 60° C. to about 200° C. for at least 0.2 hour, and preferably at a temperature of from 90° C. to about 100° C. for about one to two hours to convert the gel to pigmentary monoclinic bismuth vanadate.
• the pH of the suspension must be maintained at a pH of from 2.2 to 6.0, and preferably from a pH of 3.0 to 3.5, by adding a suitable acid or base as needed.
• Acids suitable for use include nitric, sulfuric, hydrochloric, hydrobromic or phosphoric. Based suitable for use include aqueous sodium hydroxide or potassium hydroxide. It will be understood that if temperatures above about 100° C. are used, the heating must be carried out under pressure. In addition, when the ratio of Bi to VO 4 is 0.9:1 to 1.0:1.0, the digested pigment must be washed after the heating step by suspending it in water for 15 to 30 minutes at 50° C. to 100° C. while holding the pH at 8.0 to 9.5 with an aqueous base selected from sodium hydroxide and potassium hydroxide. Preferably the digested pigment will be washed in water for 15 minutes at 70° C.
• the pigment is filtered, washed and dried, e.g., at about 130° C.
• the product is bright primrose yellow bismuth vanadate which is entirely in the monoclinic phase as identified by X-ray diffraction.
• the pH adjustment can be made after the gel has been removed from the suspension.
• the gel should be resuspended in water. Once the pH of the gel has been properly adjusted, the gel under certain circumstances is stable for up to about a week at room temperature.
• the alkali vanadate solution by dissolving a pentavalent vanadium compound such as V 2 O 5 , Na 3 VO 4 , Na 4 V 2 O 7 , NaVO 3 , or K 3 VO 4 in an aqueous base selected from sodium hydroxide and potassium hydroxide.
• a pentavalent vanadium compound such as V 2 O 5 , Na 3 VO 4 , Na 4 V 2 O 7 , NaVO 3 , or K 3 VO 4
• an aqueous base selected from sodium hydroxide and potassium hydroxide.
• the bismuth vanadate pigment After the bismuth vanadate pigment has been prepared by the process of this invention, its lightfastness may be improved by encapsulation in a dense amorphous coating of silica or a treatment with aluminum pyrophosphate. Coatings can be applied in accordance with known processes, such as those taught in U.S. Pat. No. Re 27,818 (reissue of U.S. Pat. No. 3,437,502) to Werner; U.S. Pat. No. 3,639,133 to Linton; U.S. Pat. No. 3,370,971 to Linton; and of U.S. Pat. No. 3,885,366 to Iler.
• a mixture is prepared by combining the following ingredients in a mixing tee:
• the mixing tee has inside diameters of 0.118 in. for the bismuth nitrate opening, 0.192 in. for the sodium vanadate opening, and 0.192 in. for the exit.
• the bismuth nitrate enters on the leg.
• the solutions are mixed in about 15 minutes when a pressure of about 15 psi is applied across the tee.
• Sufficient HNO 3 is added to ingredient (i) or aqueous NaOH to ingredient (ii) so that the pH of the mixture of the two will be about 1.5 to 2.0.
• the mixture is squirted into a 45 gal. tank containing 7 gal. of water which has been adjusted to a pH of 2.2 with HNO 3 .
• the contents of the tank are stirred for several minutes, and the pH is adjusted to 3.2 with 2.0N NaOH.
• the contents are then stirred for 15 minutes, filtered, and washed with 20 gal. of water and refiltered.
• the bismuth vanadate gel is collected from the filter cloth, and is stirred into a tank containing 70 lb. of water, which has been adjusted to a pH of 3.1 with HNO 3 .
• the contents of the tank are heated to 95° C. in about 40 minutes and held at that temperature and a pH of 3.1 for 120 minutes.
• the product, pigmentary bismuth vanadate is isolated by filtration, washed twice with 20 gal. of water, and dried at 140° C.
• This example shows that encapsulating bismuth vanadate pigment with silica improves its lightfastness as determined by Fade-Ometer® exposures.
• a mixture is prepared by combining the following ingredients in a 1 mm ID mixing tee at 40 psi over a period of about two minutes:
• HNO 3 Sufficient HNO 3 is added to ingredient (i) or aqueous NaOH to ingredient (ii) so that the pH of the mixture of the two will be about 1.5-2.0.
• the mixture is squirted into a large beaker containing 1200 ml. of water adjusted to a pH of 2.7 with HNO 3 .
• the contents of the beaker are stirred and the pH is adjusted to 3.4 with 0.5N NaOH.
• the contents are then stirred for 10 minutes, filtered, washed with 1000 ml. of water, and refiltered.
• a bismuth vanadate gel is collected from the filter paper, is stirred into a beaker containing 3000 ml.
• the suspension is then heated to 85° C. and aluminum sulfate (18.0 g. Al 2 (SO 4 ) 3 .18H 2 O in 240 ml. water) is added.
• the pH of the suspension is adjusted to 4.0 with 1.0N NaOH, the sodium pyrophosphate (6.0 g. in 120 ml. of water) and aluminum sulfate (6.0 g. Al 2 (SO 4 ) 3 .18H 2 O in 120 ml. of water) are added to the suspension.
• the pH is adjusted to 7.0 with aqueous NaOH over a thirty-minute period.
• the suspension is filtered, washed and dried at 110° C. to yield an aluminum phosphate coated yellow pigment. Intensity and lightfastness before and after coating are shown in Table II.
• This example shows that treatment of bismuth vanadate pigment with aluminum phosphate improves lightfastness as determined by Fade-Ometer® exposures.
• a mixture is prepared by combining the following ingredients in a 1 mm ID mixing tee at 40 psi over a period of about two minutes:
• Sufficient HNO 3 is added to ingredient (i) or aqueous NaOH to ingredient (ii) so that the pH of the mixture of the two will be about 1.5 to 2.0.
• the mixture is squirted into a 4-liter beaker containing 1200 ml. of water which has been adjusted to a pH of 3.0 with HNO 3 .
• the contents of the beaker are stirred for one minute and the pH is adjusted to 3.4 with 0.5N NaOH.
• the mixture is than stirred for 15 minutes, filtered, washed with 500 ml. of water, and refiltered.
• a bismuth vanadate gel (Sample A) is collected from the filter paper, and is stirred into a beaker containing 1600 ml.
• Sample B is prepared according to the procedure used for Sample A except that 42.0 g., instead of 40.0 g., of Bi(NO 3 ) 3 .5H 2 O is used.
• Sample C is prepared by combining the following ingredients in a 1 mm ID mixing tee at 40 psi over a period of about 2 minutes:
• V 2 O 5 (15.0 g.) dissolved in 600 ml. of water containing 53.0 g. of NaOH, then diluted to 800 ml. with water to give a solution of sodium vanadate plus sodium hydroxide.
• HNO 3 Sufficient HNO 3 is added to ingredient (iii) of aqueous NaOH to ingredient (iv) so that the pH of the mixture of the two will be about 1.5 to 2.0.
• the mixture is squirted into a 4-liter beaker containing 1200 ml. of water which has been adjusted to a pH of 2.2 with HNO 3 .
• the contents of the beaker are stirred for one minute and the pH is adjusted to 3.3 with 0.5N NaOH.
• the mixture is then stirred for 15 minutes, filtered, washed with 500 ml. of water, and refiltered.
• a bismuth vanadate gel is collected from the filter paper and is stirred into a beaker containing 500 ml. of water.
• the pH of the mixture is adjusted to 3.3 to 3.4 with HNO 3 or NaOH and is boiled for 90 minutes while the pH is kept constant at 3.3 to 3.4.
• a bismuth vanadate pigment is isolated by filtration, washed with 500 ml. of water, and heated at 130° C. until dry.
• Sample D is prepared according to the procedure used for Sample A, except that 46.0 g., instead of 40.0 g., of Bi(NO 3 ) 3 .5H 2 O is used.
• Sample E is prepared by combining the following ingredients in a 1 mm ID mixing tee at 40 psi over a period of 2 minutes.
• V 2 O 5 (15.0 g.) dissolved in 600 ml. water containing 53.30 g. NaOH, then diluted to 800 ml. with water to give a solution of sodium vanadate plus sodium hydroxide.
• HNO 3 Sufficient HNO 3 is added to ingredient (v) or aqueous NaOH to ingredient (vi) so that the pH of the mixture of the two will be about 1.5 to 2.0.
• the mixture is squirted into a 4-liter beaker containing 1200 ml. of water which has been adjusted to a pH of 2.2 with HNO 3 .
• the contents of the beaker are stirred for one minute and the pH is adjusted to 3.3 with 0.5N NaOH.
• the mixture is then stirred for 15 minutes and filtered.
• a bismuth vanadate gel is collected from the filter paper.
• the gel is stirred into a beaker containing 500 ml. of water and the pH of the mixture is adjusted to 3.1 with HNO 3 or NaOH.
• the mixture is boiled for 120 minutes while its pH is held at 3.1.
• the bismuth vanadate pigment is isolated by filtration and resuspended in 400 ml. of water. The temperature is then raised to 50° C. and the pH raised to 8.0 and held there for 10 minutes.
• a bismuth vanadate pigment is isolated by filtration, washed with 500 ml. of water, and heated to 130° C. until dried.
• a mixture is prepared by combining the following ingredients in a mixing tee:
• V 2 O 5 (2.049 lb.) dissolved in 31.94 liters of water containing 7.210 lb. NaOH, then diluted to 51.1 liters with water, to give a solution of sodium vanadate plus sodium hydroxide.
• the mixing tee has inside diameters of 0.118 in. for the bismuth nitrate opening, 0.192 in. for the sodium vanadate opening, and 0.192 in. for the exit.
• the bismuth nitrate enters on the leg.
• the solutions are mixed in about 15 minutes when a pressure of about 15 psi is applied across the tee.
• Sufficient HNO 3 is added to ingredient (i) or aqueous NaOH to ingredient (ii) so that the pH of the mixture of the two will be about 1.5 to 2.0.
• the mixture is squirted into a 45 gal. tank containing 7 gal. of water which has been adjusted to a pH of 2.2 with HNO 3 .
• the contents of the tank are stirred for several minutes, and the pH is adjusted to 3.2 with 2.0N NaOH.
• the contents are then stirred for 15 minutes, filtered and washed with 20 gal. of water and refiltered.
• a mixture is prepared by combining the following ingredients in a mixing tee:
• V 2 O 5 (51.6 g) dissolved in 1718 ml of water containing 178 g of NaOH, then diluted to 2750 ml to give a solution of sodium vanadate plus sodium hydroxide.
• HNO 3 Sufficient HNO 3 is added to ingredient (i) or aqueous NaOH to ingredient (ii) so that the pH of the mixture of the two will be about 1.5-2.0.
• the mixture is squirted into a strike jar containing 1500 ml of water which has been adjusted to a pH of 2.2 with HNO 3 .
• the mixture is stirred and the pH adjusted to 3.2 with 0.5N NaOH.
• the stirring is continued for 15 minutes.
• the pH is adjusted to 3.1 with 1N HNO 3 and heated to 95° C for 3 hrs. with pH kept between 2.8 and 3.5 using 0.5N NaOH or 1.0N HNO 3 .
• the bismuth vanadate precipitate is filtered, washed to 2000 ⁇ resistance and dried.
• the product has 66.2% green filter reflectance and 4.5% Fade-Ometer darkening.
• a mixture is prepared by combining the following ingredients in a 1 mm ID mixing tee at a pressure of 40 psi over about a 2-minute period.
• HNO 3 Sufficient HNO 3 is added to ingredient (i) or NaOH to ingredient (ii) so that the pH of the mixture of the two will be between 1.5 and 2.0.
• the mixture is squirted into a 4 l beaker containing 1200 ml of distilled water which had been adjusted to a pH of 2.7 with HNO 3 .
• the suspension is filtered and washed.
• the bismuth vanadate gel is converted to monoclinic bismuth vanadate by hydrothermal digestion at pH 3.0 to 3.5 at 100° C. Twelve-month Florida exposure in thermosetting acrylic lacquer showed good performance versus commercial yellow pigment.
• a mixture is prepared by combining the following ingredients in a 1 mm ID mixing tee at a pressure of 40 psi over about a 2-minute period.
• V 2 O 5 (14.8g) dissolved in 345 ml of 2.3N (NaOH) and diluted to 800 ml with distilled water.
• HNO 3 is added to ingredient (i) or NaOH to ingredient (ii) so that the pH of the final mixture is 3.2.
• the suspension is stirred and pH monitored at 4.0-6.0 during most of the strike.
• Final pH is 3.2.
• the pH is adjusted immediately to 3.0 with HNO 3 and stirred at room temperature for 30 minutes.
• the suspension is filtered and washed.
• Intensity of the product as measured by green filter reflectance is 67.3% and % darkening after 44 hr. Fade-Ometer exposure is 5.8%.
• a mixture is prepared by combining the following ingredients in a 1 mm ID mixing tee at 15 psi to give a molar ratio of Bi 3+ to VO 4 3- of 0.95:1.00.
• V 2 O 5 (15.0 g) dissolved in 600 ml of distilled water containing 52.0 g NaOH and diluted to 800 ml to give a solution of sodium vanadate and sodium hydroxide.
• Sufficient HNO 3 is added to ingredient (i) or NaOH to ingredient (ii) so that the pH of mixture will be between 1.5 and 2.5.
• the mixture is squirted under 15 psi pressure into a 4 l beaker containing 1200 ml of distilled water adjusted to pH 2.2 with dilute HNO 3 .
• the contents of the beaker are stirred, after 2 minutes the pH is adjusted to 3.2 with 2N NaOH and stirred 15 minutes.
• About one-third of the suspended gel is removed and is designated Sample A (See Table V).
• the remainder is filtered and divided into 2 parts identified as Samples B and D, respectively.
• Sample B is filtered only and Sample D is washed once in 200 ml of distilled water.
• Sample A's pH is adjusted to 3.2 and it is heated to 90°-100° C with pH maintained between 2.8 and 3.5 at a volume of 700-800 ml for 2-3 hours. After conversion of gel to crystalline material the pH is raised to 8.5 for 15 minutes with temperature >60° C. Bismuth vanadate is then filtered, washed twice and dried at 110° C.
• Samples B and D are resuspended, respectively, in 700-800 ml of distilled water and pH adjusted to 3.2. Samples B and D are converted at the same temperature, time and pH as Sample A. After conversion, Sample B is divided in half. One half retains identification as Sample B, is filtered, washed and dried at 110° C. The other half is identified as Sample C, has pH adjusted to 9.0 at temperature >60° C for 15 minutes, is filtered, washed and dried at 110° C.
• Sample D is divided in half. One half retains identification as Sample D, is filtered, washed and dried. The other half is identified as Sample E and is treated in the same fashion as Sample C.
• Sample F is prepared according to the procedure of Sample A except that 78.5 g of Bi(NO 3 ) 3 .5H 2 O is used, giving a molar ratio of Bi 3+ to VO 4 3- of 0.98:1.00.
• the gel suspension is filtered and divided in half. One half retains identification Sample F and the other half is identified as Sample G and is washed once in 250 ml of distilled water.
• Sample F is converted according to the procedure of Sample A, is filtered, washed and dried at 110° C.
• Sample G is converted according to the procedure of Sample A, is filtered, washed and dried at 110° C.
• a mixture is prepared by combining the following ingredients in a 1 mm ID mixing tee at 15 psi to give a molar ratio of Bi 3+ to VO 4 3- of 1.00:1.00.
• Sufficient HNO 3 is added to ingredient (i) or NaOH to ingredient (ii) so that the pH of the mixture will be between 1.5 and 2.5.
• the mixture is squirted under 40 psi pressure into a 4 l beaker containing 1000 ml of distilled water which had been adjusted to pH 3.3 with 2N HNO 3 .
• the gel suspension is stirred for a minute and the pH adjusted to 3.3 with 0.5N NaOH.
• About 1300 ml of the mixture is removed and identified as Sample H in Table V.
• the remainder of the mixture, identified as Sample J is filtered and washed twice with ⁇ 500 ml of distilled water.
• Sample H is diluted to 2000 ml, pH is adjusted to 3.3, heated at 100° C for 4 hrs. to convert the gel to crystalline material, filtered, washed and dried at 110° C.
• Sample J is converted according to procedure of Sample H except for 3 hrs. instead of 4.
• the crystalline material is filtered, washed and dried at 110° C.
• Sample K is prepared by the procedure of Sample H except 88.0 g Bi(NO 3 ) 3 .5H 2 O is used and Na 3 VO 4 is prepared from V 2 O 5 and NaOH. This gives a molar ratio of Bi 3+ to VO 4 3- of 1.10:1.00.
• the gel suspension is divided in half. One-half retains identification Sample K; the other half is identified Sample L.
• Sample K gel suspension pH is adjusted to 3.2, temperature is raised to 98°-100° C for 21/2 hours, pH is maintained at 3.3. Product is filtered, washed and dried at 140° C.
• Sample L is filtered and resuspended in distilled water to give 700 ml volume. Sample L is converted, filtered, washed and dried by the procedure of Sample K.

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Cited By (22)

Citations (1)

• 1977
  • 1977-05-09 US US05/794,392 patent/US4115141A/en not_active Expired - Lifetime
  • 1977-06-21 BE BE178609A patent/BE855909A/fr unknown

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